In an article entitled, Ultraviolet Electroluminesence in Aluminum Nitride, Applied Physics Letters, Vol. 28, No. 7, April 1976 n-type conductivity conducting aluminum nitride was described as being grown on sapphire substrates at high temperatures in excess of 1800.degree. C. The technique that was employed while successful in producing aluminum nitride, required a nucleating layer on the sapphire substrate and the nucleating layer had to be formed at a substantially different temperature in a different piece of equipment, further a presynthesized sintered source of aluminum nitride was required.
In U.S. Pat. No. 3,634,149 aluminum nitride is reported to have been grown on silicon carbide substrates in a temperature range of 1800.degree.-2300.degree. C. In this instance the source material for the growth of the aluminum nitride is presynthesized aluminum nitride and further carbide crystals which are difficult to reproducibly grow in useful sizes appear to be the only reproducible substrate for this method. Extensive literature exists on the growth of aluminum nitride on sapphire and other substrates at low temperatures in the vicinity of 1500.degree. C. by vapor transport using chlorine or fluorine compounds and plasma techniques. This literature is reported in the review article in the Journal of Crystal Growth, Vol. 34, p. 263, 1976. The electronic properties, however, of low temperature grown aluminum nitride have not been satisfactory for device use. The properties appear to be very high resistance in the vicinity of 10.sup.13 ohms per cm and the layers grown in many cases appear to have a tendency to craze or crack and sometimes peel from the substrate.